Low Energy Proton Beam Lithography with a Thin Oxygen-Etch Barrier Layer

Abstract

Low energy protons in the several keV energy range have very limited penetration depths into polymer films. This limitation necessitates the use of very thin oxygen-etch barrier layers and of dry image development by oxygen reactive ion etching. For negative tone images, the etch-barrier layers were deposited patternwise by proton-beam-induced polymerizations of organo-metallic compounds, followed with dry image development by oxygen reactive ion etching. For positive tone images, the etch-barrier layers were deposited (prior to patternwise exposure to proton beams) on top of polymer films by plasma polymerizations of organo-metallic compounds, or by evaporation or sputtering of certain metals. Hydrogen atoms and/or protons react with metal atoms in the etch barrier layers to yield volatile metal hydrides, making the exposed areas more vulnerable to oxygen reactive ion etching, and providing positive tone images after image development. Sub-keV electrons can replace low energy protons for fabrications of positive-tone polymer images. In these processes, almost any kind of carbonaceous polymer film can be used as the imaged material. With a bright ion gun available, the exposure times could be less than a second, yielding high aspect ratio and high resolution polymer patterns. © 1984, The Electrochemical Society, Inc. All rights reserved.